From 6070bf3596f3b5a54091a08d5b2bc90c143dc264 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Mon, 8 Nov 2010 11:20:49 +0900 Subject: kernel: Constify temporary variable in roundup() Fix build error with GCC 3.x caused by commit b28efd54 "kernel: roundup should only reference arguments once" by constifying temporary variable used in that macro. Signed-off-by: Tetsuo Handa Suggested-by: Andrew Morton Acked-by: Eric Paris Signed-off-by: James Morris --- include/linux/kernel.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 450092c1e35f..b526947bdf48 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -60,7 +60,7 @@ extern const char linux_proc_banner[]; #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) #define roundup(x, y) ( \ { \ - typeof(y) __y = y; \ + const typeof(y) __y = y; \ (((x) + (__y - 1)) / __y) * __y; \ } \ ) -- cgit v1.2.3 From 074e61ec3751da9ab88ee66d3818574556c03489 Mon Sep 17 00:00:00 2001 From: James Morris Date: Wed, 10 Nov 2010 09:01:31 +1100 Subject: kernel: add roundup() code comment from akpm Add roundup() code comment from akpm. Signed-off-by: Andrew Morton Signed-off-by: James Morris --- include/linux/kernel.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index b526947bdf48..3f648d204c37 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -58,6 +58,8 @@ extern const char linux_proc_banner[]; #define FIELD_SIZEOF(t, f) (sizeof(((t*)0)->f)) #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) + +/* The `const' in roundup() prevents gcc-3.3 from calling __divdi3 */ #define roundup(x, y) ( \ { \ const typeof(y) __y = y; \ -- cgit v1.2.3 From eaf06b241b091357e72b76863ba16e89610d31bd Mon Sep 17 00:00:00 2001 From: Dan Rosenberg Date: Thu, 11 Nov 2010 14:05:18 -0800 Subject: Restrict unprivileged access to kernel syslog The kernel syslog contains debugging information that is often useful during exploitation of other vulnerabilities, such as kernel heap addresses. Rather than futilely attempt to sanitize hundreds (or thousands) of printk statements and simultaneously cripple useful debugging functionality, it is far simpler to create an option that prevents unprivileged users from reading the syslog. This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the dmesg_restrict sysctl. When set to "0", the default, no restrictions are enforced. When set to "1", only users with CAP_SYS_ADMIN can read the kernel syslog via dmesg(8) or other mechanisms. [akpm@linux-foundation.org: explain the config option in kernel.txt] Signed-off-by: Dan Rosenberg Acked-by: Ingo Molnar Acked-by: Eugene Teo Acked-by: Kees Cook Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index b526947bdf48..fc3da9e4da19 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -293,6 +293,7 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, unsigned int interval_msec); extern int printk_delay_msec; +extern int dmesg_restrict; /* * Print a one-time message (analogous to WARN_ONCE() et al): -- cgit v1.2.3 From 968ab1838a5d48f02f5b471aa1d0e59e2cc2ccbc Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 15 Nov 2010 13:37:37 -0800 Subject: include/linux/kernel.h: Move logging bits to include/linux/printk.h Move the logging bits from kernel.h into printk.h so that there is a bit more logical separation of the generic from the printk logging specific parts. Signed-off-by: Joe Perches Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 245 +------------------------------------------------ 1 file changed, 1 insertion(+), 244 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index fc3da9e4da19..b6de9a6f7018 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -17,13 +17,11 @@ #include #include #include +#include #include #include #include -extern const char linux_banner[]; -extern const char linux_proc_banner[]; - #define USHRT_MAX ((u16)(~0U)) #define SHRT_MAX ((s16)(USHRT_MAX>>1)) #define SHRT_MIN ((s16)(-SHRT_MAX - 1)) @@ -110,31 +108,6 @@ extern const char linux_proc_banner[]; */ #define lower_32_bits(n) ((u32)(n)) -#define KERN_EMERG "<0>" /* system is unusable */ -#define KERN_ALERT "<1>" /* action must be taken immediately */ -#define KERN_CRIT "<2>" /* critical conditions */ -#define KERN_ERR "<3>" /* error conditions */ -#define KERN_WARNING "<4>" /* warning conditions */ -#define KERN_NOTICE "<5>" /* normal but significant condition */ -#define KERN_INFO "<6>" /* informational */ -#define KERN_DEBUG "<7>" /* debug-level messages */ - -/* Use the default kernel loglevel */ -#define KERN_DEFAULT "" -/* - * Annotation for a "continued" line of log printout (only done after a - * line that had no enclosing \n). Only to be used by core/arch code - * during early bootup (a continued line is not SMP-safe otherwise). - */ -#define KERN_CONT "" - -extern int console_printk[]; - -#define console_loglevel (console_printk[0]) -#define default_message_loglevel (console_printk[1]) -#define minimum_console_loglevel (console_printk[2]) -#define default_console_loglevel (console_printk[3]) - struct completion; struct pt_regs; struct user; @@ -187,11 +160,6 @@ static inline void might_fault(void) } #endif -struct va_format { - const char *fmt; - va_list *va; -}; - extern struct atomic_notifier_head panic_notifier_list; extern long (*panic_blink)(int state); NORET_TYPE void panic(const char * fmt, ...) @@ -245,115 +213,8 @@ extern int func_ptr_is_kernel_text(void *ptr); struct pid; extern struct pid *session_of_pgrp(struct pid *pgrp); -/* - * FW_BUG - * Add this to a message where you are sure the firmware is buggy or behaves - * really stupid or out of spec. Be aware that the responsible BIOS developer - * should be able to fix this issue or at least get a concrete idea of the - * problem by reading your message without the need of looking at the kernel - * code. - * - * Use it for definite and high priority BIOS bugs. - * - * FW_WARN - * Use it for not that clear (e.g. could the kernel messed up things already?) - * and medium priority BIOS bugs. - * - * FW_INFO - * Use this one if you want to tell the user or vendor about something - * suspicious, but generally harmless related to the firmware. - * - * Use it for information or very low priority BIOS bugs. - */ -#define FW_BUG "[Firmware Bug]: " -#define FW_WARN "[Firmware Warn]: " -#define FW_INFO "[Firmware Info]: " - -/* - * HW_ERR - * Add this to a message for hardware errors, so that user can report - * it to hardware vendor instead of LKML or software vendor. - */ -#define HW_ERR "[Hardware Error]: " - -#ifdef CONFIG_PRINTK -asmlinkage int vprintk(const char *fmt, va_list args) - __attribute__ ((format (printf, 1, 0))); -asmlinkage int printk(const char * fmt, ...) - __attribute__ ((format (printf, 1, 2))) __cold; - -/* - * Please don't use printk_ratelimit(), because it shares ratelimiting state - * with all other unrelated printk_ratelimit() callsites. Instead use - * printk_ratelimited() or plain old __ratelimit(). - */ -extern int __printk_ratelimit(const char *func); -#define printk_ratelimit() __printk_ratelimit(__func__) -extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, - unsigned int interval_msec); - -extern int printk_delay_msec; -extern int dmesg_restrict; - -/* - * Print a one-time message (analogous to WARN_ONCE() et al): - */ -#define printk_once(x...) ({ \ - static bool __print_once; \ - \ - if (!__print_once) { \ - __print_once = true; \ - printk(x); \ - } \ -}) - -void log_buf_kexec_setup(void); -#else -static inline int vprintk(const char *s, va_list args) - __attribute__ ((format (printf, 1, 0))); -static inline int vprintk(const char *s, va_list args) { return 0; } -static inline int printk(const char *s, ...) - __attribute__ ((format (printf, 1, 2))); -static inline int __cold printk(const char *s, ...) { return 0; } -static inline int printk_ratelimit(void) { return 0; } -static inline bool printk_timed_ratelimit(unsigned long *caller_jiffies, \ - unsigned int interval_msec) \ - { return false; } - -/* No effect, but we still get type checking even in the !PRINTK case: */ -#define printk_once(x...) printk(x) - -static inline void log_buf_kexec_setup(void) -{ -} -#endif - -/* - * Dummy printk for disabled debugging statements to use whilst maintaining - * gcc's format and side-effect checking. - */ -static inline __attribute__ ((format (printf, 1, 2))) -int no_printk(const char *s, ...) { return 0; } - -extern int printk_needs_cpu(int cpu); -extern void printk_tick(void); - -extern void asmlinkage __attribute__((format(printf, 1, 2))) - early_printk(const char *fmt, ...); - unsigned long int_sqrt(unsigned long); -static inline void console_silent(void) -{ - console_loglevel = 0; -} - -static inline void console_verbose(void) -{ - if (console_loglevel) - console_loglevel = 15; -} - extern void bust_spinlocks(int yes); extern void wake_up_klogd(void); extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */ @@ -390,22 +251,6 @@ extern enum system_states { #define TAINT_CRAP 10 #define TAINT_FIRMWARE_WORKAROUND 11 -extern void dump_stack(void) __cold; - -enum { - DUMP_PREFIX_NONE, - DUMP_PREFIX_ADDRESS, - DUMP_PREFIX_OFFSET -}; -extern void hex_dump_to_buffer(const void *buf, size_t len, - int rowsize, int groupsize, - char *linebuf, size_t linebuflen, bool ascii); -extern void print_hex_dump(const char *level, const char *prefix_str, - int prefix_type, int rowsize, int groupsize, - const void *buf, size_t len, bool ascii); -extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type, - const void *buf, size_t len); - extern const char hex_asc[]; #define hex_asc_lo(x) hex_asc[((x) & 0x0f)] #define hex_asc_hi(x) hex_asc[((x) & 0xf0) >> 4] @@ -419,94 +264,6 @@ static inline char *pack_hex_byte(char *buf, u8 byte) extern int hex_to_bin(char ch); -#ifndef pr_fmt -#define pr_fmt(fmt) fmt -#endif - -#define pr_emerg(fmt, ...) \ - printk(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) -#define pr_alert(fmt, ...) \ - printk(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_crit(fmt, ...) \ - printk(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_err(fmt, ...) \ - printk(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warning(fmt, ...) \ - printk(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warn pr_warning -#define pr_notice(fmt, ...) \ - printk(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__) -#define pr_info(fmt, ...) \ - printk(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) -#define pr_cont(fmt, ...) \ - printk(KERN_CONT fmt, ##__VA_ARGS__) - -/* pr_devel() should produce zero code unless DEBUG is defined */ -#ifdef DEBUG -#define pr_devel(fmt, ...) \ - printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#else -#define pr_devel(fmt, ...) \ - ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) -#endif - -/* If you are writing a driver, please use dev_dbg instead */ -#if defined(DEBUG) -#define pr_debug(fmt, ...) \ - printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#elif defined(CONFIG_DYNAMIC_DEBUG) -/* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */ -#define pr_debug(fmt, ...) \ - dynamic_pr_debug(fmt, ##__VA_ARGS__) -#else -#define pr_debug(fmt, ...) \ - ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; }) -#endif - -/* - * ratelimited messages with local ratelimit_state, - * no local ratelimit_state used in the !PRINTK case - */ -#ifdef CONFIG_PRINTK -#define printk_ratelimited(fmt, ...) ({ \ - static DEFINE_RATELIMIT_STATE(_rs, \ - DEFAULT_RATELIMIT_INTERVAL, \ - DEFAULT_RATELIMIT_BURST); \ - \ - if (__ratelimit(&_rs)) \ - printk(fmt, ##__VA_ARGS__); \ -}) -#else -/* No effect, but we still get type checking even in the !PRINTK case: */ -#define printk_ratelimited printk -#endif - -#define pr_emerg_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_EMERG pr_fmt(fmt), ##__VA_ARGS__) -#define pr_alert_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_ALERT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_crit_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_CRIT pr_fmt(fmt), ##__VA_ARGS__) -#define pr_err_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_ERR pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warning_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__) -#define pr_warn_ratelimited pr_warning_ratelimited -#define pr_notice_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_NOTICE pr_fmt(fmt), ##__VA_ARGS__) -#define pr_info_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_INFO pr_fmt(fmt), ##__VA_ARGS__) -/* no pr_cont_ratelimited, don't do that... */ -/* If you are writing a driver, please use dev_dbg instead */ -#if defined(DEBUG) -#define pr_debug_ratelimited(fmt, ...) \ - printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__) -#else -#define pr_debug_ratelimited(fmt, ...) \ - ({ if (0) printk_ratelimited(KERN_DEBUG pr_fmt(fmt), \ - ##__VA_ARGS__); 0; }) -#endif - /* * General tracing related utility functions - trace_printk(), * tracing_on/tracing_off and tracing_start()/tracing_stop -- cgit v1.2.3 From dc88e46029486ed475c71fe1bb696d39511ac8fe Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Tue, 23 Nov 2010 17:50:31 -0500 Subject: lib: hex2bin converts ascii hexadecimal string to binary Similar to the kgdb_hex2mem() code, hex2bin converts a string to binary using the hex_to_bin() library call. Changelog: - Replace parameter names with src/dst (based on David Howell's comment) - Add 'const' where needed (based on David Howell's comment) - Replace int with size_t (based on David Howell's comment) Signed-off-by: Mimi Zohar Acked-by: Serge E. Hallyn Acked-by: David Howells Signed-off-by: James Morris --- include/linux/kernel.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index a35b4f7332f0..d0fbc043de60 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -265,6 +265,7 @@ static inline char *pack_hex_byte(char *buf, u8 byte) } extern int hex_to_bin(char ch); +extern void hex2bin(u8 *dst, const char *src, size_t count); /* * General tracing related utility functions - trace_printk(), -- cgit v1.2.3 From 71a9048448de302d1e968f336de01060d02fae71 Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Wed, 12 Jan 2011 16:59:35 -0800 Subject: include/linux/kernel.h: abs(): fix handling of 32-bit unsigneds on 64-bit Michal reports: In the framebuffer subsystem the abs() macro is often used as a part of the calculation of a Manhattan metric, which in turn is used as a measure of similarity between video modes. The arguments of abs() are sometimes unsigned numbers. This worked fine until commit a49c59c0 ("Make sure the value in abs() does not get truncated if it is greater than 2^32:) , which changed the definition of abs() to prevent truncation. As a result of this change, in the following piece of code: u32 a = 0, b = 1; u32 c = abs(a - b); 'c' will end up with a value of 0xffffffff instead of the expected 0x1. A problem caused by this change and visible by the end user is that framebuffer drivers relying on functions from modedb.c will fail to find high resolution video modes similar to that explicitly requested by the user if an exact match cannot be found (see e.g. Fix this by special-casing `long' types within abs(). This patch reduces x86_64 code size a bit - drivers/video/uvesafb.o shrunk by 15 bytes, presumably because it is doing abs() on 4-byte quantities, and expanding those to 8-byte longs adds code. testcase: #define oldabs(x) ({ \ long __x = (x); \ (__x < 0) ? -__x : __x; \ }) #define newabs(x) ({ \ long ret; \ if (sizeof(x) == sizeof(long)) { \ long __x = (x); \ ret = (__x < 0) ? -__x : __x; \ } else { \ int __x = (x); \ ret = (__x < 0) ? -__x : __x; \ } \ ret; \ }) typedef unsigned int u32; main() { u32 a = 0; u32 b = 1; u32 oldc = oldabs(a - b); u32 newc = newabs(a - b); printf("%u %u\n", oldc, newc); } akpm:/home/akpm> gcc t.c akpm:/home/akpm> ./a.out 4294967295 1 Reported-by: Michal Januszewski Cc: Rolf Eike Beer Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d0fbc043de60..57dac7022b63 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -143,9 +143,22 @@ extern int _cond_resched(void); #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0) -#define abs(x) ({ \ - long __x = (x); \ - (__x < 0) ? -__x : __x; \ +/* + * abs() handles unsigned and signed longs, ints, shorts and chars. For all + * input types abs() returns a signed long. + * abs() should not be used for 64-bit types (s64, u64, long long) - use abs64() + * for those. + */ +#define abs(x) ({ \ + long ret; \ + if (sizeof(x) == sizeof(long)) { \ + long __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } else { \ + int __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } \ + ret; \ }) #define abs64(x) ({ \ -- cgit v1.2.3 From 3e7d344970673c5334cf7b5bb27c8c0942b06126 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 13 Jan 2011 15:45:56 -0800 Subject: mm: vmscan: reclaim order-0 and use compaction instead of lumpy reclaim Lumpy reclaim is disruptive. It reclaims a large number of pages and ignores the age of the pages it reclaims. This can incur significant stalls and potentially increase the number of major faults. Compaction has reached the point where it is considered reasonably stable (meaning it has passed a lot of testing) and is a potential candidate for displacing lumpy reclaim. This patch introduces an alternative to lumpy reclaim whe compaction is available called reclaim/compaction. The basic operation is very simple - instead of selecting a contiguous range of pages to reclaim, a number of order-0 pages are reclaimed and then compaction is later by either kswapd (compact_zone_order()) or direct compaction (__alloc_pages_direct_compact()). [akpm@linux-foundation.org: fix build] [akpm@linux-foundation.org: use conventional task_struct naming] Signed-off-by: Mel Gorman Cc: Andrea Arcangeli Cc: KOSAKI Motohiro Cc: Rik van Riel Acked-by: Johannes Weiner Cc: Andy Whitcroft Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 57dac7022b63..5a9d9059520b 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -600,6 +600,13 @@ struct sysinfo { #define NUMA_BUILD 0 #endif +/* This helps us avoid #ifdef CONFIG_COMPACTION */ +#ifdef CONFIG_COMPACTION +#define COMPACTION_BUILD 1 +#else +#define COMPACTION_BUILD 0 +#endif + /* Rebuild everything on CONFIG_FTRACE_MCOUNT_RECORD */ #ifdef CONFIG_FTRACE_MCOUNT_RECORD # define REBUILD_DUE_TO_FTRACE_MCOUNT_RECORD -- cgit v1.2.3 From 2ce802f62ba32a7d95748ac92bf351f76affb6ff Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 20 Jan 2011 12:06:35 +0100 Subject: lockdep: Move early boot local IRQ enable/disable status to init/main.c During early boot, local IRQ is disabled until IRQ subsystem is properly initialized. During this time, no one should enable local IRQ and some operations which usually are not allowed with IRQ disabled, e.g. operations which might sleep or require communications with other processors, are allowed. lockdep tracked this with early_boot_irqs_off/on() callbacks. As other subsystems need this information too, move it to init/main.c and make it generally available. While at it, toggle the boolean to early_boot_irqs_disabled instead of enabled so that it can be initialized with %false and %true indicates the exceptional condition. Signed-off-by: Tejun Heo Acked-by: Peter Zijlstra Acked-by: Pekka Enberg Cc: Linus Torvalds LKML-Reference: <20110120110635.GB6036@htj.dyndns.org> Signed-off-by: Ingo Molnar --- include/linux/kernel.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 5a9d9059520b..d07d8057e440 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -243,6 +243,8 @@ extern int test_taint(unsigned flag); extern unsigned long get_taint(void); extern int root_mountflags; +extern bool early_boot_irqs_disabled; + /* Values used for system_state */ extern enum system_states { SYSTEM_BOOTING, -- cgit v1.2.3 From 7ef88ad561457c0346355dfd1f53e503ddfde719 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 24 Jan 2011 14:45:10 -0600 Subject: BUILD_BUG_ON: make it handle more cases BUILD_BUG_ON used to use the optimizer to do code elimination or fail at link time; it was changed to first the size of a negative array (a nicer compile time error), then (in 8c87df457cb58fe75b9b893007917cf8095660a0) to a bitfield. This forced us to change some non-constant cases to MAYBE_BUILD_BUG_ON(); as Jan points out in that commit, it didn't work as intended anyway. bitfields: needs a literal constant at parse time, and can't be put under "if (__builtin_constant_p(x))" for example. negative array: can handle anything, but if the compiler can't tell it's a constant, silently has no effect. link time: breaks link if the compiler can't determine the value, but the linker output is not usually as informative as a compiler error. If we use the negative-array-size method *and* the link time trick, we get the ability to use BUILD_BUG_ON() under __builtin_constant_p() branches, and maximal ability for the compiler to detect errors at build time. We also document it thoroughly. Signed-off-by: Rusty Russell Cc: Jan Beulich Acked-by: Hollis Blanchard --- include/linux/kernel.h | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index d07d8057e440..864712f3653d 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -575,12 +575,6 @@ struct sysinfo { char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */ }; -/* Force a compilation error if condition is true */ -#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition)) - -/* Force a compilation error if condition is constant and true */ -#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)])) - /* Force a compilation error if a constant expression is not a power of 2 */ #define BUILD_BUG_ON_NOT_POWER_OF_2(n) \ BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0)) @@ -592,6 +586,33 @@ struct sysinfo { #define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); })) #define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); })) +/** + * BUILD_BUG_ON - break compile if a condition is true. + * @cond: the condition which the compiler should know is false. + * + * If you have some code which relies on certain constants being equal, or + * other compile-time-evaluated condition, you should use BUILD_BUG_ON to + * detect if someone changes it. + * + * The implementation uses gcc's reluctance to create a negative array, but + * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments + * to inline functions). So as a fallback we use the optimizer; if it can't + * prove the condition is false, it will cause a link error on the undefined + * "__build_bug_on_failed". This error message can be harder to track down + * though, hence the two different methods. + */ +#ifndef __OPTIMIZE__ +#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)])) +#else +extern int __build_bug_on_failed; +#define BUILD_BUG_ON(condition) \ + do { \ + ((void)sizeof(char[1 - 2*!!(condition)])); \ + if (condition) __build_bug_on_failed = 1; \ + } while(0) +#endif +#define MAYBE_BUILD_BUG_ON(condition) BUILD_BUG_ON(condition) + /* Trap pasters of __FUNCTION__ at compile-time */ #define __FUNCTION__ (__func__) -- cgit v1.2.3 From 1765e3a4933ea0870fabd755feffc5473c4363ce Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 24 Jan 2011 14:45:10 -0600 Subject: Remove MAYBE_BUILD_BUG_ON Now BUILD_BUG_ON() can handle optimizable constants, we don't need MAYBE_BUILD_BUG_ON any more. Signed-off-by: Rusty Russell --- include/linux/kernel.h | 1 - 1 file changed, 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 864712f3653d..e2f4d6af2125 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -611,7 +611,6 @@ extern int __build_bug_on_failed; if (condition) __build_bug_on_failed = 1; \ } while(0) #endif -#define MAYBE_BUILD_BUG_ON(condition) BUILD_BUG_ON(condition) /* Trap pasters of __FUNCTION__ at compile-time */ #define __FUNCTION__ (__func__) -- cgit v1.2.3 From ffbbf2da9e578dc7b7ae4f945412c4b74f54b20e Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Mon, 31 Jan 2011 09:29:14 -0800 Subject: kernel.h: fix kernel-doc warning Fix kernel-doc warning in kernel.h from commit 7ef88ad56145 ("BUILD_BUG_ON: make it handle more cases"): Warning(include/linux/kernel.h:605): No description found for parameter 'condition' Warning(include/linux/kernel.h:605): Excess function parameter 'cond' description in 'BUILD_BUG_ON' Signed-off-by: Randy Dunlap Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/kernel.h') diff --git a/include/linux/kernel.h b/include/linux/kernel.h index e2f4d6af2125..2fe6e84894a4 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -588,7 +588,7 @@ struct sysinfo { /** * BUILD_BUG_ON - break compile if a condition is true. - * @cond: the condition which the compiler should know is false. + * @condition: the condition which the compiler should know is false. * * If you have some code which relies on certain constants being equal, or * other compile-time-evaluated condition, you should use BUILD_BUG_ON to -- cgit v1.2.3